I got the the alternator back from the place rebuilding it only to learn there were no problems with it. They told me the output was right at 14v. The battery is holding a full charge. Anyone have any ideas on what may be causing the drain on the battery?

Some history:

When the battery was drained, I had been sitting in heavy morning traffic for about an hour in 72 degree F North Georgia weather. I reached my destination, and had no problems. I went to move the car less than 15 minutes after arriving, and, when attempting to start, learned the battery was dead. I let it sit for almost 8 hours, but it still wouldn't start. We used jumper cables (prior to learning it is not a good idea) and got it running. Upon getting the car restarted, the battery light came on (it was not on before), went off when accelerating, but came back on when letting off the gas or sitting still. Upon reaching the shop, we removed the battery (per specs) and placed it on a charger outside the car. The "eye" was black, which meant to charge the battery according to the label. It charged up to capacity and performed well under load on a load tester. We let it recharge for over an hour and placed it back into the car. The car started up no problem, and no warning lights were on. We tested voltage at the battery and it read 9v, which is what led us to believe the alternator was failing.

It is a factory battery and the "eye" is reading fine - no problems.

I have not recently installed anything, electronic or otherwise.

The car has been sitting more than normal, but has been driven at least 3-4 times a week.

The car has just under 85000 miles on it.

I have kept all the service items up to date, including the major service items at a local, reputable BMW certified mechanic.

The temperatures have been warm and very humid ranging from the high 60s (F) at night to high 80s during the day.

I haven't run over anything or taken any damage.

Until now, I have had no problems. Of course it is out of warranty, and I am out of work, so any assistance would be greatly appreciated.